Monolithic foundation system with homopolymer/ressistannt aggregate pavement with a semi-continuous configuration

ABSTRACT

This invention relates to a monolithic foundation ( 1 ) system with homopolymer/resist ant aggregate pavement with a semi-continuous configuration, which uses a pavement with load transfer elements ( 5 ) for the induction of joints. It is essentially characterized in that it comprises a foundation ( 1 ) having high-density expanded polystyrene blocks, which supports a semi -continuous cement concrete pavement, the pavement formwork being formed by the polystyrene blocks of the foundation. Each one of the load transfer plates ( 5 ) is comprised of two anchors ( 6 ) with two rebars ( 7 ) for alignment of a joint inductor ( 8 ), and a ball joint ( 9 ) which, at the load support moment, rotates anticlockwise and, at the support moment generated by the load transfer plates, performs a clockwise movement. The said ball joint releases the concrete slabs ( 4 ) from stress caused by bending/traction at the moment of load transfer, allowing the foundation to be unaffected by bending moments resulting from the load and thus making the slab ( 4 ) work essentially with compression stress. The existence of the said ball joints enables the foundation to be obtained by the said polystyrene blocks.

SCOPE OF THE INVENTION

This invention relates to a monolithic foundation system with homopolymer/resistant aggregate pavement with a semi-continuous configuration, more specifically to a semi-continuous cement concrete pavement having joints formed by load transfer plates, with a structural strength which, by itself, absorbs, degrades and transmit loads, while withstanding the forces exerted thereon as well as the abrasion caused thereby, without differential settlements on the joint axis, also serving as a wearing course, the said pavement being laid on a foundation which is independent of the natural soil and acting as both a base and a sub-base.

PRIOR ART

Today, surfaces intended namely for large public areas and mainly for roads and airports can be made with rigid and flexible pavements. Cement concrete pavements and bituminous pavements are already known, each of them having its own implementation rules in accordance with the materials employed.

In the case of rigid pavements, special attention must be given to the occurrence of sudden changes in the characteristics of the sub-bed, particularly to the presence of expansive soils and thick layers of soft clay. In this type of pavement, for the above mentioned reasons, special attention is given to the foundations. Therefore, several materials are used, such as a stable form of stones, pebbles, gravel and grit and sand with variable thickness, and/or other materials such as cement boards. However, the cleaning of the soil must be previously carried out as far as its vegetable layer is concerned, with the subsequent levelling of the soil for the laying of the several layers comprising the foundation.

There are various methods for calculating the foundation, which take into consideration the foundation categories, the land classes, the materials used for the bed layer and constitution of the platform. This results in complex foundations which are not always able to maintain the desired integrity.

All of the aforementioned types of pavements require a specific foundation for supporting them.

Furthermore, rigid pavements also comply with well-established rules. The standards usually considered for determining the pavement characteristics are closely related to aspects such as traffic, loads, sub-bed support and drainage. One of the main problems to be solved is the differential settlements between adjacent concrete slabs in pavements laid on elastic soils. For this purpose, load transfer elements are considered which minimize the loads projected on the foundation and prevent the settlement of the slabs. Another problem to be solved in the design of a rigid cement concrete pavement concerns the sealing of the joints between slabs. The basic function of the sealing of the induction slot in the joints of a concrete pavement is to prevent the intrusion of water and incompressible solid materials, such as sand, small stones and other foreign substances. Water infiltration through the joint has damaging effects on the durability of a pavement, essentially because it is the main cause of pumping, which consists of the deterioration of the foundation layer by expulsion of the grindings of which it is constituted, meaning that the board becomes unprotected and thus subject to degradation (this being known as the pumping phenomenon).

SUMMARY OF THE INVENTION

In order to solve and/or minimize the aforementioned inconveniences, the applicants have devised a monolithic system of foundation/pavement, which uses a foundation comprised of polystyrene blocks and a pavement having special load transfer elements.

Therefore, an object of the invention is the use of a semi-continuous cement concrete pavement having joints formed by load transfer plates, with a structural strength which, by itself, absorbs, degrades and transmits loads, while withstanding the forces exerted thereon as well as the abrasion caused thereby, without differential settlements on the joint axis, also serving as a wearing course, the said pavement being laid on a foundation which is independent of the natural soil and acting as both a base and a sub-base for supporting the said semi-continuous concrete pavement.

The load transfer elements used by the system of the invention are basically the elements of prior art disclosed in Portuguese patent no. 102947, to which improvements have been made so that the use of polystyrene blocks in the foundations is permitted. Patent PT 102947 is herein incorporated for reference purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

The description hereunder is based on the attached drawings which, without any restrictive character, represent the following:

FIG. 1 is a schematic illustration of the system of the invention;

FIG. 2 is a schematic illustration of an expansion and contraction joint;

FIG. 3 is a schematic illustration of a construction joint;

FIG. 4 is another schematic illustration of the system of the invention;

FIG. 5 is a perspective view of the load transfer plate of the system of the invention; and

FIG. 6 is a main elevation of the load transfer plate of the system of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Prior to pavement concreting, an appropriate foundation is built to receive the area of the pavement to be concreted, being comprised of several strips, each of them being formed by a sequence of slabs. In turn, the slabs must be confined by a formwork. Finally, the concreting of the slabs is carried out.

As can be observed in the figures, the foundation (1) is obtained by the application of high-density expanded polystyrene blocks which, as a homopolymer, remains stable throughout the useful life of the system and, in terms of its technical specifications (density, deformation modulus), has a steady behaviour without modification of the Westergaard modulus: K/cm³. The foundation (1) ensures the carrying capacity of the overall structure and must be designed to that end. The polystyrene blocks having densities and dimensions according to the design are laid over the natural soil (2). Surface levelling errors should not exceed 5 mm in a 3 m ruler.

In order to obtain an appropriate formwork, it is not necessary to fill it with inert materials of various granulometries and with possible frames, as is the case in prior art.

With the base and sub-base foundation (1) used in the system of the invention, since it is formed by high-density expanded polystyrene, it has specific technical characteristics which remain unaltered throughout the useful life of this material and which are essentially the following:

-   -   Maintaining its physical and chemical properties     -   Preserving density/weight/volume,     -   Maintaining the elasticity and deformation modulus (Kg/cm³)     -   Not altering its properties with the thermal gradient     -   Remaining sealed     -   Maintaining a uniform support     -   Useful life of more than 100 years     -   Reducing the friction coefficient at the moment of concrete         contraction     -   Allowing manual laying without the aid of heavy machinery     -   Serving as a formwork, for the purpose of concreting the         pavement (3)     -   Providing slopes for water runoff     -   In special circumstances, a box opening is not required     -   Providing gutters for water runoff     -   Using pumped concrete, which permits the laying of the concrete         with high slumps     -   Simplifying the laying of the concrete because, since it is         pumped, it allows easier access to the concreting corridor     -   Increasing the speed of execution

The use of polystyrene blocks replaces the base and sub-base of conventional foundations. These blocks also provide a formwork which is suitable for a continuous concreting. The level of the formworks will be according to the initial design elevation. Horizontal tolerance will be between 1 and 2 cm in length. The length of the formwork elements is limited in order to allow levelling and layout according to the design elevation.

After the laying of the foundation (1) and consequently the formwork, the pavement (3) can be concreted according to the established work specification.

The concreting process comprises the following steps:

Preparation

The layout of the longitudinal profile will be realized on site with the aid of topographic precision instruments. The prescribed levels are verified by stakes placed solidly in the ground, outside the concreting corridor, at maximum intervals of 50 m, so that a rigorous longitudinal profile is formed parallel to the final elevation of the slab to be executed. In the case of curves, the distance between the stakes is reduced in order to exactly follow the profile of the design. The placing of the stakes must be carried out at least one day before the concreting operation. Unless there is a local impediment, to be recognized by the inspection authority, the preparation of the joints and the placement of the load transfer plates should precede the concreting by a distance of around 50 m, in order to ensure continuous implementation.

The release of water on the surface will be ensured by a draining system which will be implemented simultaneously with the laying of the foundation (1) (polystyrene blocks).

Preparation of the Concreting Corridor Against Water Leakages from the Concrete

In order to prevent any water absorption from the concrete to the foundation (1), the foundation should be always covered with a sliding complex of approximately 0.2 mm and coverings of 20 cm.

Composition of the Concrete

The composition of the concrete will be sent to the inspection authority to be approved thereby. It must be in compliance with the pre-established conditions for each specific project.

Manufacturing, Transport and On-Site Implementation Manufacturing

Manufacturing will preferably take place at the construction site and the equipment will have sufficient capacity to ensure a continuous laying operation.

Transport

The type of transport will be subject to approval by the inspection authority, whether in a cement truck mixer or in a dump truck.

On-Site Implementation

On-site implementation will be carried out with vibratory equipment, possibly complemented by a corrective ruler.

All surface charges or recharges are prohibited.

In special locations, the concrete may be laid and hand vibrated with a vibrating needle.

All the edges of the slabs along the formworks will have to be vibrated using a needle vibrator.

Atmospheric Conditions

Concreting will not be permitted during days of heavy rain.

Surface Treatment

The surface treatment of the coating will be made by brushing the fresh concrete with brushes previously approved by the inspection authority.

Transverse and Longitudinal Joints

All the transverse and longitudinal joints are provided with load transfer plates.

Contraction and expansion joints are according to FIG. 2. The sawing depth is of at least 2 cm.

Construction Joints

These are according to FIG. 3. The construction joints are established at the end of each daily production or in the case of interruption of the concreting operation. As can be observed, the face of the joint must be flat and perpendicular to the surface of the coating. As soon as the concreting operation is restarted, the said joints are placed concrete against concrete, the face of the preceding slab being bathed with an anti-adherent agent, such as Antisol, in order to provide an effective separation.

The pavement generically illustrated as (3) is formed by several slabs (4) which are provided with load transfer plates (5). The said plates (5) are comprised of two anchors (6) with two rebars (7) for alignment of a joint inductor (8), and a ball joint (9) which, at the load support moment, rotates anticlockwise and, at the support moment generated by the load transfer plates (5), performs a clockwise movement. This ball joint (9) is positioned under the joint inductor (8) and its centre is aligned with the vertical axis of the joint formed by the said inductor (8).

The said ball joint (9) releases the concrete slabs (4) from stress caused by bending/traction at the moment of load transfer, allowing the foundation (1) to be unaffected by bending moments resulting from the load and thus making the slab (4) work essentially with compression stress, thereby ensuring a safety coefficient much higher than the normal one and a long life of the foundation (1) of the slab (4). The ball joint (9) releasing the concrete slabs (4) from stress caused by bending/traction at the moment of load transfer will thus allow the said concrete slabs (4) to work for a longer period of time with compression, i.e. releasing them from permanent stress and filtering most of the vibrations caused by rolling loads.

The geometric features of the slabs (4) are as follows:

-   -   Nominal thickness: variable (conditioned by the forces to be         exerted thereon)     -   Side-grade: usually 2% (see cross-sectional profiles of the         design)     -   Nominal length: from 5 to 8 m (conditioned by the forces to be         exerted thereon)     -   Nominal width: from 5 to 8 m (conditioned by the forces to be         exerted thereon)

The said slabs (4) will be subject to:

-   -   1—Occasional rolling and static loads;     -   2—Horizontal stress caused by concrete contraction;     -   3—Horizontal stress caused by friction;     -   4—Breaking of slabs (4) caused by the supports on the joints         axis due to load transmission; and     -   5—Liquid or water infiltration phenomena, such as the pumping         phenomenon.

In conclusion, this invention relates to a pavement (3) which has been successfully tested in all kinds of adverse conditions, having now a new conception of supports for joints, which consists of providing the load transfer plates (5) with ball joints (9) which, as previously mentioned, release the concrete slabs (4) from stress caused by bending/traction at the moment of load transfer, allowing the foundation (1) to remain unaffected by bending moments resulting from the load and thus making the slab (4) work essentially with compression stress. In fact, it is due to the ball joints (9) that foundations (1) with polystyrene blocks can be obtained.

Joint sealing is required for protecting the foundation (1) against chemical agents/diluents. This sealing is guaranteed by placement of the joint inductor (8), which has a certain slope for water (liquid) runoff, together with the use of a silicone-type insulating material (with two components) injected on the joint over the inductor (8) in order to provide complete insulation.

Likewise, the foundation (1) must be coated along its upper and lateral parts with a plastic material. This material allows a reduction from about 2.5 to 0.5 in the friction coefficient of the slab (4) concrete when contracting and it also insulates the polystyrene blocks against any chemical attack resulting from spillages on the pavement surface (3).

ECONOMIC ASPECTS

With this system of the invention, it is possible to reduce costs by constructing and using these pavements, as opposed to the conventional solutions, such as for example:

-   -   it is not necessary to invest in heavy machinery for a box         opening;     -   excavations;     -   application of selected inert materials;     -   spreading of materials;     -   compactation of inert materials;     -   levelling of inert materials;         i.e. all the work relating to the laying of selected soils to         build a foundation (1) (base and sub-base).

Considering that the foundation (1) can be laid manually, the whole building concept relating to the base and sub-base for the laying of pavements (3) is profoundly revolutionized.

The durability (useful life of more than 100 years) with the complete absence of maintenance operations will release financial resources, both in public and private entities, for investment in other areas which are also a priority.

The low investment required for this technology, together with its long durability, makes it accessible to all entities which carry out work of this nature.

Lisbon, 30 Jan. 2009 

1. A monolithic foundation system with homopolymer/resistant aggregate pavement with a semi-continuous configuration, which uses a pavement with load transfer elements for the induction of joints, comprising a foundation having high-density expanded polystyrene blocks, which supports a semi-continuous cement concrete pavement, the pavement formwork being formed by the polystyrene blocks of the foundation.
 2. A monolithic foundation/pavement system according to claim 1, wherein the polystyrene blocks having dimensions as established in the design are manually laid.
 3. A monolithic foundation/pavement system according to claim 1, further comprising a load transfer plate comprised of two anchors with two rebars for alignment of a joint inductor and a ball joint which, at the load support moment, rotates anticlockwise and, at the support moment generated by the load transfer plates, performs a clockwise movement.
 4. A method for the execution of a foundation/pavement according to claim 3, comprising: releasing, by said ball joint, of the concrete slabs from stress caused by bending/traction at the moment of load transfer, allowing the foundation to remain unaffected by bending moments resulting from the load and thus making the slab work essentially with compression stress.
 5. The method for the execution of a foundation/pavement according to claim 4, further comprising positioning the said ball joint under the joint inductor and its centre is aligned with the vertical axis of the joint formed by the said inductor.
 6. The method for the execution of a foundation/pavement according to claim 4, further comprising sealing the joint for protecting the foundation against chemical agents/diluents, having a silicone-type insulating material injected over the inductor in order to provide complete insulation.
 7. The method for the execution of a foundation/pavement according to claim 4, further comprising coating the foundation along its upper and lateral parts with a plastic material, in order to reduce from about 2.5 to 0.5 the friction coefficient of the slab concrete when contracting and simultaneously protect the polystyrene blocks from possible spillages of liquids at the surface. 